The mapping of interferon-induced proteins and phosphoproteins from HeLa S3 cells

Proteins induced by recombinant equine interferon-beta 1 within equine peripheral blood mononuclear cells and polymorphonuclear neutrophilic granulocytes

Peripheral blood mononuclear cells (PBMC) and polymorphonuclear neutrophilic granulocytes (PMN) as well as embryonic equine dermal fibroblasts and the equine fibroblast line E. Derm which were used as controls, were treated with recombinant equine interferon-beta 1 (rEqIFN-beta 1) in vitro which induced the expression of different proteins in these cells. A 74 kDa protein was induced in PBMC and an 82 kDa protein was additionally found in the equine fibroblast E. Derm cell line following treatment with rEqFN-beta 1. Both proteins reacted with anti-mouse and anti-human Mx protein antisera in immunoblot tests. The 74 kDa and perhaps the 82 kDa components may thus represent equine 'Mxanalogous proteins'. The 74 kDa protein was only detected in PBMC of ten out of 20 horses examined. The induction of Mx protein in the horse by Type 1 interferon may therefore resemble that in the mouse, where Mx protein is involved in selective resistance to influenza virus. The influence of rEqIFN-beta 1 on protein expression in equine PBMC and PMN was monitored by metabolic labeling and 2-D gel electrophoresis. Proteins of 82, 74, 58 and 40 kDa were induced in PBMC following exposure to rEqIFN-beta 1. A constitutively expressed 35 kDa protein, however, was no longer demonstrable upon treatment with interferon. None of the proteins induced within PBMC was found in highly purified PMN treated with interferon. PMN exposed to rEqIFN-beta 1 synthesized four proteins in the range of 25 to 27 kDa. These proteins have not been described in interferon-treated PMN of any other species.

2-Aminopurine inhibits the double-stranded RNA-dependent protein kinase both in vitro and in vivo

The autophosphorylation of interferon (IFN)-induced double-stranded RNA-dependent p68 protein kinase (PKR) and phosphorylation of the alpha-subunit of the translation initiation factor eIF-2 were inhibited by 10 mM 2-aminopurine in vitro. High concentrations of ATP overcame the inhibition. Kinetic studies indicated that 2-aminopurine is a competitive inhibitor with respect to ATP, suggesting that these two molecules bind the same site on the kinase. Treatment of HeLa cells with poly(I):poly(C) stimulated PKR autophosphorylation in vivo. The stimulated activity was inhibited by 10 mM 2-aminopurine to approximately the same extent as the in vitro inhibition.